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DUBAI (Reuters) - Bahrain prosecutors on Monday filed new charges against a man believed by rights activists to be the Gulf state's most prominent jailed democracy campaigner, Nabeel Rajab, after the New York Times published an op-ed under his byline.

The prosecutor of the Gulf state's northern region, Mohammed Salah, said a man had been questioned over a complaint from the cybercrime unit accusing him of "publishing a column in a foreign newspaper in which he deliberately broadcast news, statements and false rumors that undermine the kingdom's prestige and stature".

Salah did not identify the man or name the newspaper, but a rights group and a lawyer said the statement clearly referred to Rajab, who had been in jail since June on charges related to anti-government tweets published last year, including one accusing the security forces of torturing detainees.

Rajab was a leading figure in a 2011 pro-democracy uprising led by Bahrain's Shi'ite Muslim majority and he has been repeatedly detained.

In the New York Times column, published on Sunday, Rajab addressed readers in the first person, saying he was writing from a "Bahraini jail cell where I have been detained, largely in isolation, since the beginning of summer".

The column said Bahrain was a country "that has subjected its people to imprisonment, torture and even death for daring to desire democracy".

Bahrain denies any systematic abuse by police and says it has installed cameras at interrogation centers to guard against wrongdoing by security personnel. The Sunni-led government accuses the opposition of stirring sectarian hatred in the kingdom and of serving the interests of its rival, Shi'ite Iran.

The prosecutor's statement said the suspect had denied the new charges. It reported the unidentified man as saying he could not have made any comments to any party since he was in jail.

Law enforcement authorities in Bahrain, as in other Gulf Arab states, sometimes issue statements about investigations or indictments in security cases without naming the accused.

The Bahrain Institute for Rights and Democracy said in a statement that Rajab's lawyer had been refused access to attend the interrogation of his client.

Rajab faces a prison sentence of up to 13 years if convicted on the older charges levied against him.

(Reporting by Sami Aboudi; Editing by William Maclean and Gareth Jones)